With rapid increasing amount of TV channels and TV programs in recent years, it is possible that more than one program of interest are broadcast on different channels simultaneously. The viewer has to choose one program among those or frequently switch between different channels. Moreover, it is difficult for modern humans to watch programs at fixed time daily or weekly in their busy lives. Scheduled recording is the most convenient method to solve these problems. The TV program subscribers may watch desired programs after the broadcast. When digital video recorders equipped with hard drives are developed, the video data capacity may easily reach several tens of hours. Hence, it usually occurs that more and more programs are recorded in the hard drive and the viewer has no time to review all the recording contents. For example, advertisements inserted in the TV programs are bothersome and always be skipped by pressing the forward button or rotating the speed knob in the forward direction. Besides, the advertisements waste the space on the recording media.
Some recording methods are developed to remove the advertisements by means of image analysis. The advertisements may be detected according to black frames or audio discontinuity. However, the accuracy varies with the contents of the programs and the advertisements. US 2006/0020961 A1 and Taiwanese Patent No. I255142 teach methods for detection of advertisements using the features that the start portions and end portions of the program sections usually repeat, or the advertisements are usually shown in fixed time intervals. However, video signals of TV programs are too complicated and changeable to be accurately recognized and analyzed. Misjudgments usually occur during the advertisement detection which can also be a problem. Although manual operation can reduce the misjudgments, great amount of staff costs derive from numerous channels and broadcast stations and long-time detection. How to effectively detect the advertisements inserted in the TV programs is desired to solve the problems.